Using openFDA can be a breeze, if you know how to construct good queries. This short guide will get you started with {openFDA}, and show you how to put together more complicated queries. We start by loading openFDA.

library(openFDA)

#> ! OpenFDA API key set.
#> ℹ You can retrieve the key with the following code:
#>   `keyring::key_get(service = "OPENFDA_KEY", user = "openFDA")`

The openFDA API

The openFDA API makes public FDA data available from a simple, public API. Users of this API have access to FDA data on food, human and veterinary drugs, devices, and more. You can read all about it at their website. The API limits results sets to 1000 records. To access over 1000 results, you’d usually need to manually submit multiple requests which skip past larger and larger chunks of the dataset (see online for more info).

With this package, however, that can be handled for you. By default, openFDA() will ask you if you want to retrieve all possible results. However, asking for user input isn’t possible when in a vignette. Additionally, we don’t want to do paging for these examples, as our searches get lots of results. Therefore, to prevent paging, we set the package-level option openFDA.paging to "never". Now openFDA() will automatically not perform paging, even when it’s possible.

options(openFDA.paging = "never")

A simple openFDA query

The simplest way to query the openFDA API is to identify the endpoint you want to use and provide other search terms. For example, this snippet retrieves 2 records about adverse events in the drugs endpoint. The empty search string ("") means the results will be non-specific.

search <- openFDA(search = "",
                  endpoint = "drug-event",
                  limit = 2)
#> ! openFDA returned more results (20692690) than your `limit` (2).
#> ℹ With 2 results per page, pagination will require 10,346,345 queries to
#>   retrieve all of these results. This will take at least 11h 58m 30s.
search
#> <httr2_response>
#> GET https://api.fda.gov/drug/event.json?search=&limit=2
#> Status: 200 OK
#> Content-Type: application/json
#> Body: In memory (3923 bytes)

The warning given about pagination is because we searched on the whole dataset, but used limit to only pull out the first two results. We can suppress this warning by setting paging_verbosity to "quiet". Now we won’t page the whole dataset, because paging == "never", and we won’t get that warning either:

search <- openFDA(search = "",
                  endpoint = "drug-event",
                  limit = 2,
                  paging = "never",
                  paging_verbosity = "quiet")
search
#> <httr2_response>
#> GET https://api.fda.gov/drug/event.json?search=&limit=2
#> Status: 200 OK
#> Content-Type: application/json
#> Body: In memory (3923 bytes)

Instead of setting the paging and paging_verbosity arguments each time you call the function, it is better to set the package-level option for these behaviours. You can do this with any function that edits options:

options(
  openFDA.paging = "never",
  openFDA.paging_verbosity = "quiet"
)

openFDA results

The function returns an {httr2} response object, with attached JSON data. We use httr2::resp_body_json() to extract the underlying data.

json <- httr2::resp_body_json(search)

If you don’t specify a field to count on, the JSON data has two sections - meta and results.

Results

For non-count queries, this will be a set of records which were found in the endpoint and match your search term.

json$results
#> [[1]]
#> [[1]]$safetyreportid
#> [1] "5801206-7"
#> 
#> [[1]]$transmissiondateformat
#> [1] "102"
#> 
#> [[1]]$transmissiondate
#> [1] "20090109"
#> 
....

Results when `count`-ing

If you set the count query, then the openFDA API will not return full records. Instead, it will count the number of records for each member in the openFDA field you specified for count. For example, let’s look at drug manufacturers in the Drugs@FDA endpoint for "paracetamol".

count <- openFDA(search = "openfda.generic_name:ketamine",
                 endpoint = "drug-drugsfda",
                 count = "openfda.manufacturer_name.exact") |>
  httr2::resp_body_json()
count$results
#> [[1]]
#> [[1]]$term
#> [1] "Baxter Healthcare Corporation"
#> 
#> [[1]]$count
#> [1] 1
#> 
#> 
#> [[2]]
#> [[2]]$term
....

Using `count` to make a time series

You can count on fields with a date to create a time series. This is demonstrated on the openFDA website, where they count the number of received records per day in the drug/event endpoint. With the openFDA package, you could do it in R like this:

resp <- openFDA(endpoint = "drug-event", count = "receiptdate")
# Extract the counts from the response as a data frame
data <- httr2::resp_body_json(resp, simplifyDataFrame = TRUE) |>
  purrr::pluck("results")
data$date <- as.Date.character(data$time, format = "%Y%m%d")
# Sort on date column
data <- data[order(data$date), ]
# Restrict to data from 2000 to 2019
data <- data[data$date >= as.Date("2019-01-01") &
                     data$date < as.Date("2019-12-31"), ]
# Plot
plot(x = data$date, y = data$count,
     xlab = "Date", ylab = "Number of adverse events reported")

A scatter plot of date (on x axis) against number of adverse events reported to the FDA (y-axis).

Using search terms

We can increase the complexity of our query using the search parameter, which lets us search against specific openFDA API fields. These fields are harmonised to different degrees in each API, which you will need to check online.

Searching on one field

You can provide search strategies to openFDA() as single strings. They are constructed as [FIELD_NAME]:[STRING], where FIELD_NAME is the openFDA field you want to search on. If your STRING contains spaces, you must surround it with double quotes, or openFDA will search against each word in the string. So, for example, a search for drugs with the class "thiazide diuretic" should be formatted as "openfda.pharm_class_epc:\"thiazide diuretic\"", or the API will collect all drugs which have the words "thiazide" or "diuretic" in their established pharmacological class (EPC).

Note that there are helpers in the package (i.e. construct_search_term()) for assembling search terms; they are discussed below.

Let’s do an unrefined search first:

search_unrefined <- openFDA(
  search = "openfda.pharm_class_epc:thiazide diuretic",
  endpoint = "drug-drugsfda",
  limit = 1
)
httr2::resp_body_json(search_unrefined)$meta$results$total
#> [1] 234

Let’s compare this to our refined search, where we add double-quotes around the search term:

search_refined <- openFDA(
  search = "openfda.pharm_class_epc:\"thiazide diuretic\"",
  endpoint = "drug-drugsfda",
  limit = 1
)
httr2::resp_body_json(search_refined)$meta$results$total
#> [1] 125

As you can see, the unrefined search picked up 109 more results, most of which would have probably been non-thiazide diuretics.

Searching on multiple fields

The openFDA API also lets you search on various fields at once, to construct increasingly more specific queries. You can either write your own complex search queries, or let the package do (some of) the heavier lifting for you.

Write your own search term

Using the guides on the openFDA website, you can put together your own query. For example, the following query looks for up to 5 records which were submitted by Walmart and are taken orally. We can use {purrr} functions to extract a brand name for each record. Note that though a single record can have multiple brand names, we are choosing to only extract the first one.

search_term <- "openfda.manufacturer_name:Walmart+AND+openfda.route=oral"
search <- openFDA(search = search_term,
                  endpoint = "drug-drugsfda",
                  limit = 5)
json <- httr2::resp_body_json(search)
purrr::map(json$results, .f = \(x) {
  purrr::pluck(x, "openfda", "brand_name", 1)
})
#> [[1]]
#> [1] "NAPROXEN"
#> 
#> [[2]]
#> [1] "BASIC CARE LANSOPRAZOLE"
#> 
#> [[3]]
#> [1] "NAPROXEN SODIUM AND DIPHENHYDRAMINE HCL"
#> 
#> [[4]]
#> [1] "PURELAX"
#> 
#> [[5]]
#> [1] "ANTI-DIARRHEAL/ANTI-GAS MULTI-SYMPTOM RELIEF"

Let `openFDA()` construct the search term

In openFDA(), you can provide a named character vector with many field/search term pairs to the search parameter. The function will automatically add double quotes ("") around your search terms, if you’re providing field/value pairs like this.

search <- openFDA(search = c("openfda.generic_name" = "amoxicillin"),
                  endpoint = "drug-drugsfda",
                  limit = 1)
paste("Number of results:", httr2::resp_body_json(search)$meta$results$total)
#> [1] "Number of results: 57"

You can include as many fields as you like, as long as you only provide each field once. By default, the terms are combined with an OR operator in openFDA(). The below search strategy will therefore pick up all entries in Drugs@FDA which are taken by mouth.

search <- openFDA(search = c("openfda.generic_name" = "amoxicillin",
                             "openfda.route" = "oral"),
                  endpoint = "drug-drugsfda",
                  limit = 1)
paste("Number of results:", httr2::resp_body_json(search)$meta$results$total)
#> [1] "Number of results: 7175"

Pre-construct a search term

You can use format_search_term() to pre-generate strings to pass to openFDA() as search:

format_search_term(
  c("openfda.generic_name" = "amoxicillin", "openfda.route" = "oral")
)
#> [1] "openfda.generic_name:%22amoxicillin%22+openfda.route:%22oral%22"

Sometimes you will want to combine multiple search terms with AND operators. To do this, set the mode argument to "and":

search_term <- format_search_term(
  c("openfda.generic_name" = "amoxicillin", "openfda.route" = "oral"),
  mode = "and"
)
search_term
#> [1] "openfda.generic_name:%22amoxicillin%22+AND+openfda.route:%22oral%22"

search <- openFDA(search = search_term,
                  endpoint = "drug-drugsfda",
                  limit = 1)
paste("Number of results:", httr2::resp_body_json(search)$meta$results$total)
#> [1] "Number of results: 54"

Wildcards

You can use the wildcard character "*" to match zero or more characters. For example, we could take the prototypical ending to a common drug class - e.g. the sartans, which are angiotensin-II receptor blockers - and see which manufacturers are most represented in Drugs@FDA for this class. When using wildcards, either pre-format the string yourself without double-quotes or use format_search_term() with exact = FALSE. If you try to search with both double-quotes and the wildcard character, you will get a 404 error from openFDA. In the code block below, we use a wildcard to find all drugs with generic names ending with "sartan", and count on the manufacturer names.

search_term <- format_search_term(c("openfda.generic_name" = "*sartan"),
                                  exact = FALSE)
search <- openFDA(search = search_term,
                  count = "openfda.manufacturer_name.exact",
                  endpoint = "drug-drugsfda",
                  paging = "always")
results <- httr2::resp_body_json(search, simplifyDataFrame = TRUE) |>
        purrr::pluck("results")
head(results, n = 10)
#>                                term count
#> 1  Macleods Pharmaceuticals Limited    16
#> 2   Alembic Pharmaceuticals Limited    15
#> 3      Alembic Pharmaceuticals Inc.    14
#> 4          Aurobindo Pharma Limited    13
#> 5       Lupin Pharmaceuticals, Inc.    11
#> 6      Camber Pharmaceuticals, Inc.    10
#> 7        Mylan Pharmaceuticals Inc.     7
#> 8                   NorthStar RxLLC     7
#> 9          Solco Healthcare US, LLC     7
#> 10       Zydus Lifesciences Limited     7

It looks like "Alembic Pharmaceuticals" is very active in this space - interesting!

Large result sets

The openFDA API only returns up to 1000 results at one time. To return a results set larger than 1000 records, a basic paging system is implemented. On a per-call basis, this is controlled by the paging parameter in openFDA(). To change this behaviour for the duration of an R session, edit the option "openFDA.paging", as demonstrated above.

This argument must take one of these values:

"ask" (default; only valid if R is running interactively) - ask before performing paging
"yes" - always perform paging where necessary, but print a message to the console
"yes-quiet" - always perform paging where necessary, but don’t print a message to the console
"no" - never perform paging, but print a message to the console
"no-quiet" - never perform paging, but don’t print a message to the console

When paging is performed, openFDA() returns a list of {httr2} response objects, instead of a single response:

resps <- openFDA(search = "openfda.manufacturer_name:Pharma",
                 limit = 750,
                 endpoint = "drug-drugsfda",
                 paging = "always",
                 paging_verbosity = "verbose")
#> ! openFDA returned more results (2074) than your `limit` (750).
#> ℹ With 750 results per page, pagination will require 3 queries to retrieve all
#>   of these results. This will take at least 1s.
resps
#> [[1]]
#> <httr2_response>
#> GET https://api.fda.gov/drug/drugsfda.json?search=openfda.manufacturer_name:Pharma&limit=750
#> Status: 200 OK
#> Content-Type: application/json
#> Body: In memory (3521122 bytes)
#> 
#> [[2]]
#> <httr2_response>
#> GET https://api.fda.gov/drug/drugsfda.json?search=openfda.manufacturer_name%3APharma&limit=750&skip=0&search_after=0%3DMZeCpaABvkcavpo_4l51
#> Status: 200 OK
#> Content-Type: application/json
#> Body: In memory (3379776 bytes)
#> 
#> [[3]]
#> <httr2_response>
#> GET https://api.fda.gov/drug/drugsfda.json?search=openfda.manufacturer_name%3APharma&limit=750&skip=0&search_after=0%3DipeCpaABvkcavpo_1DOy
#> Status: 200 OK
#> Content-Type: application/json
#> Body: In memory (2829884 bytes)

Other openFDA API features

This short guide does not cover all aspects of openFDA. It is recommended that you go to the openFDA API website and check out the resources there to see information on:

openFDA